The present invention relates to a method of testing an airbag module for a vehicle and, particularly, but not exclusively, to a method of testing an airbag module for a motor vehicle such as a car.
Airbag passive restraint systems incorporating one or more airbag modules are widely used in motor vehicles to improve passenger safety and their design and manufacture is well understood by those skilled in the art. Typically, an airbag module comprises three principal components: a reaction can or reaction plate; an inflator or gas generator; and a folded airbag. These components are generally arranged with the gas generator located in an opening of the reaction can and secured together with appropriate fasteners (e.g. bolts). The mouth of the airbag is reinforced with a metal retainer ring and located over the gas generator. The gas generator is thereby encapsulated by the reaction can and the airbag. The fasteners used to secure the gas generator to the reaction can generally also secure the airbag mouth.
The reaction can is the platform upon which the gas generator is traditionally mounted and is usually manufactured as a stamped steel component capable of resisting the significant forces generated during activation of the restraint system. Reaction cans are however being increasingly manufactured from molded plastics materials such as glass filled nylon. The gas generator is typically provided as a metal body which houses a suitable igniter, a gas generant and, depending on the gas generant used, appropriate filters. The person skilled in the art will be familiar with various different types of gas generator presently used in airbag modules. The body of the gas generator is generally provided with a plurality of exit ports for permitting the release of inflation gas to the airbag. The airbag itself is folded adjacent the gas generator so as to be readily inflatable upon system activation.
In addition to the aforementioned principal components, an airbag module also incorporates an electric circuit for enabling electrical connection of the module to control circuitry of the associated restraint system. The circuit typically includes an electric igniter with an integral connector or set of lead wires for connection to the vehicle wiring harness. An airbag module also traditionally incorporates an airbag cover or door which encloses, retains and protects the airbag in its folded position until activation of the restraint system. The cover or door is configured to split along a tear seam when the airbag is inflated.
An airbag module provided in a motor vehicle such as a car is commonly mounted in a hidden compartment within, for example, the vehicle dashboard or steering wheel. In the event of the motor vehicle undergoing a predetermined deceleration (of a magnitude usually only generated during a vehicle collision), the control circuitry associated with the airbag module applies an activation signal to the electric igniter circuit so as to activate the module""s gas generator. In response to the activation signal, the igniter fires, which, in turn, ignites the gas generant. The gas generant then rapidly produces high pressure inflation gas.
The inflation gas produced by the gas generant rapidly progresses from the body of the gas generator via the exit ports and flows into the open mouth of the folded airbag. This causes the airbag to expand and displace any associated airbag cover and vehicle fascia. Where the gas generator uses a solid gas generant, the inflation gas is first directed through filters. This cools the gas and removes any burning particles therefrom which may damage the airbag or cause injury to a passenger. Once deployed, the inflated airbag provides a cushion for restraining and absorbing the kinetic energy of a passenger. An airbag passive restraint system is thereby capable of increasing the safety of vehicle passengers.
For many years it has been common practice to recycle certain components of end-of-life motor vehicles. A wide range of components such as engine blocks, exhaust pipes and brake discs have been made available by breakers as relatively inexpensive and generally reliable spare parts. This provision of spare parts not only provides consumers with an attractive alternative to purchasing new components (particularly in circumstances where the vehicle under repair is relatively old), but also has a beneficial effect on the environment through reducing waste. Indeed, in this latter regard, legislation worldwide is tending to increasingly require vehicle manufacturers to increase the proportion of vehicle components which may be recycled. Although it is presently possible to recycle the vast majority of vehicle components, constraints imposed by the technology used in airbag passive restraint systems have, in the past, prevented the recycling of airbag modules. If an airbag module needs to be replaced, the only option hithertofore has been to fit a newly manufactured module.
Unlike many components found in a motor vehicle, a visual inspection of a previously installed airbag module is not sufficient to determine suitability for future use. The current design of a module, as discussed above, is such that the airbag itself may be deployed on only one occasion. Although application of a suitable activation signal will allow determination of whether or not a previously installed airbag module is in good order, subsequent use of the module would not be possible either because the module has failed to activate (indicating its unsuitability for use) or because the module has been properly activated (rendering it unsuitable for use due to, inter alia, gas generant exhaustion). Accordingly, there has been no option in the past but to provide an airbag module as an entirely new piece of equipment. Only in this way has it been possible to effectively guarantee the safe and reliable operation of an airbag passive restraint system.
It is an object of the present invention to provide a method of testing an airbag module.
It is a further object of the present invention to provide a method of testing the suitability of a previously installed airbag module for reuse.
A first aspect of the present invention provides a method of testing an airbag module comprising the step of testing said module for exposure to a given fluid. The given fluid may be water. A number of tests are conducted on certain components of an airbag module at certain specific stages during module manufacture, however these tests alone are not sufficiently rigorous to identify the damage potentially suffered by a previously installed module during its service life. The present invention provides for the testing of module exposure to a fluid such as water. Any damage arising from exposure to water may not be apparent from a mere visual inspection or the presently used testing techniques, but may nevertheless render an airbag module inoperative or seriously degrade its performance capability.
The fluid exposure test may comprise the step of inspecting said airbag module or a swab taken therefrom by means of Atomic Absorption Spectroscopy techniques. Also, the fluid exposure test may comprise the step of inspecting said airbag module or a swab taken therefrom for deposits of a metal. Preferably, the step of inspecting for deposits of a metal comprises the step of inspecting for cations. It is desirable for the step of inspecting for deposits of a metal to quantify the amount of metal deposited. Preferably, the amount of metal deposited is quantified for a given surface area of airbag module.
It is particularly preferable for the step of inspecting for deposits of a metal to comprise the step of taking a swab from a surface of said airbag module by applying a solvent to said surface. The solvent may be 5% hydrochloric acid. Desirably, the step of inspecting for deposits of a metal further comprises the step of agitating said swab with 1% lanthanum chloride solution. In addition, the step of inspecting for deposits of a metal ideally further comprises the step of inspecting the mixture of 1% lanthanum chloride solution and swab by means of Atomic Absorption Spectroscopy so as to determine the quantity of a metal present in said mixture.
The swab may be taken from a surface of said airbag module which cannot be conveniently wiped clean. Said surface is ideally a surface of the gas generator or a surface adjacent to the gas generator. However, said surface may be a surface of the reaction can.
It is also desirable for the fluid exposure test to comprise the further step of determining a threshold quantity of a deposited metal which, if found on said airbag module, indicates an unacceptable risk of said module having been damaged through fluid exposure.
The deposited metal may be calcium or sodium.
Thus, where a motor vehicle has been immersed in water (e.g. due to flooding), a potential degradation of the vehicle""s airbag module as a result of water exposure may be detected by the present invention. If, during the testing of the airbag module in accordance with the present invention, it is determined that the airbag module has been exposed to water (or that there is an unacceptably high risk that the module has been damaged due to water exposure), then the module will not be regarded as acceptable for future use. The testing method of the present invention therefore represents a significant advancement in the art.
A second aspect of the present invention provides a method of testing an airbag module comprising the steps of: (i) locating an airbag module which has been previously installed; (ii) establishing a set of criteria to be satisfied before said airbag module is deemed acceptable for future use; and (iii) investigating against said set of criteria so as to determine the acceptability of said airbag module for future use. These steps may comprise the method of testing an airbag module for exposure to a given fluid as disclosed above.
Thus, the present invention provides means for permitting the re-use of an airbag module which has been previously installed in a motor vehicle. Where a motor vehicle has reached the end of its operational life, the present invention provides for the investigation of an airbag module installed in said vehicle against a set of criteria. If these criteria are satisfied, then the airbag module may be regarded as acceptable for future use, even though it may not be a new piece of equipment. The criteria to be satisfied may vary depending on the type of airbag module in question. Also, the criteria to be satisfied may be more stringent for old modules than for recently installed modules.